1. The Field of the Invention
The present invention relates to methods and devices for fixing graft to bone, and more specifically to fixing the anterior cruciate ligament (ACL) to the knee.
2. The Relevant Technology
Damaged or torn ligaments are commonly reconstructed using graft tissue either from a donor, referred to as an allograft, or from the patient, referred to as an autograft. Various methods are known in the arts for reattaching ligaments to bone, particularly for reconstruction of the ACL in the knee joint. Historically, graft fixation devices have been fashioned from metals, such as stainless steel and titanium alloys, but more recently, graft fixation devices are fabricated from biodegradable materials.
These newer materials do not have the same strength, toughness, or hardness as metals, and they present unsolved challenges for obtaining rigid and reliable fixation of the graft to the bone. For example, biodegradable and biological fixation devices are typically too brittle to permit impaction of a fixation pin into bone. Additionally, the low strength of these biodegradable and biological materials makes a fixation device very challenging to design such that it can be driven into bone under torque without a torsional failure occurring before the device is fully positioned to fixate a graft.
Furthermore, a biodegradable or biological fixation device can be especially difficult to remove once it is fully positioned within the bone. Because the graft reconstruction may not be perfect upon delivery of the fixation device, it is a significant disadvantage if a surgeon is unable to easily remove the fixation device in order to reposition the graft. Another problem with biodegradable or biological devices is it can be difficult to determine the position of the device within the host site under standard imaging methods.